Compatibilized compositions comprising a polyamide and polypropylene

ABSTRACT

Compatibilized compositions comprising at least one polyamide and at least propylene polymer which is at least partially modified by a polar monomer, in which compositions the propylene polymer has a melt flow index (MFI) measured according to ASTM standard D 1238-86 (230/2.16 conditions) higher than 50 g/10 min.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to compatibilized compositions comprisinga polyamide and polypropylene. It relates more particularly tocompositions exhibiting an improved combination of mechanical andadhesive properties and comprising a semiaromatic polyamide andpolypropylene of which at least a part is modified by grafting with apolar monomer, and optionally a fibrous reinforcing agent.

The invention also relates to adhesive composites of these compositionswith other materials, generally chosen from organic synthetic polymers,cellulosic products and metals, and to shaped objects made from thesecomposites.

2. Background of the Invention

Compositions based on polypropylene (called PP hereinafter) of which apart is modified by an unsaturated carboxylic acid or an anhydride ofsuch an acid and also containing a polyamide (called PA hereinafter) andglass fibres as a reinforcing material have been described in patentsUS-A-4,404,312 (Toyo Boseki K.K.) and GB-A-1,345,747 (Mitsubishi RayonCo.). These compositions exhibit advantageous mechanical properties suchas high rigidity and impact strength.

Compositions exhibiting a synergy in certain physical properties, suchas adhesiveness, are also known (U.S. Pat. No. 3,804,919 in the name ofDart Industries, Inc.). These compositions are, for example, mixtures ofunmodified PP and of PP modified by reaction with glycidyl acrylate inthe presence of an organic peroxide. The PPs are reinforced using glassfibres (examples).

However, it has not been possible, until now, to unite a satisfactorycombination of mechanical properties and of adhesiveness properties inthe same single composition.

SUMMARY OF THE INVENTION

The invention is aimed at overcoming this disadvantage and consequentlyat providing compositions based on polyamide and on polypropyleneexhibiting mechanical properties and adhesiveness properties at the sametime and to a sufficient degree.

To this end, the present invention relates to compatibilizedcompositions comprising at least one polyamide (PA) and at least onepropylene polymer (PP) which is at least partially modified by a polarmonomer, in which compositions the propylene polymer has a melt flowindex (MFI) (flow rate) measured according to ASTM standard D 1238-86(230/2.16 conditions) higher than 20 g/10 min.

The polyamides PA contained in the compatibilized compositions accordingto the invention may be chosen from the PAs derived, on the one hand,from aliphatic, alicyclic and aromatic amines and, on the other hand,from aliphatic, alicyclic and aromatic dicarboxylic acids.

Examples of amines which can be employed are hexamethylenediamine,decamethylenediamine, dodecamethylenediamine, 2,2,4- and2,4,4-trimethylhexamethylenediamines, 1,3- and1,4-bis(aminomethyl)cyclohexanes, bis(p-aminocyclohexylmethane),m-xylylenediamine and p-xylylenediamine.

Examples of acids which can be employed are adipic, suberic, sebacic,glutaric, azelaic, cyclohexanedicarboxylic, isophthalic and terephthalicacids.

The PAs involved may also be derived from acyl halides or alkyl diestersof these acids, from aminocarboxylic acids such as 6-aminocaproic,6-aminocaprylic, 6-aminolauric, 11-aminoundecanoic and12-aminododecanoic acids, for example, or else from lactams derived fromthese acids, such as, for example, ε-caprolactam and ω-dodecalactam.

These PAs can be derived from more than one amine or from more than oneacid; mixtures of different PAs can also be employed.

Examples of individual PAs which can be employed are polyhexamethyleneadipamide (nylon 66), polyhexamethylene sebacamide (nylon 610),polycapramide (nylon 6) and polydodecanamide (nylon 12).

Nevertheless, bearing in mind their good rigidity and their low moistureabsorption, the preferred PAs are the PAs obtained by polycondensationof xylylenediamines with α,ω-dicarboxylic linear aliphatic acidscontaining from 6 to 12 carbon atoms and most particularly the PAsobtained by a condensation reaction of m-xylylenediamine with adipicacid (called PAMXD6 hereinafter). Among these the PAMXD6s of mediummolecular weight such that their relative viscosity (measured in theform of a solution containing 10 g/1 at 25° C. in 96% by weightsulphuric acid) does not exceed 4 are preferred. The compromise ofmechanical and adhesiveness properties of the compatibilizedcompositions is quite remarkable when they contain PAMXD6 with arelative viscosity of between 1 and 3.

The propylene polymers PP contained in the compositions of the inventionmay be any polymers containing at least 50% and, preferably, at least80% of propylene-derived monomer units in their molecule. By way ofexamples there may be mentioned: propylene homopolymers, randomcopolymers of propylene and of at least one other alpha-olefin, such asethylene or butene, containing at least 80mol% of propylene, andso-called "block" copolymers comprising chain segments of variablelengths, each of which consists of a propylene homopolymer or of arandom copolymer such as described above.

At least a part of the PP forming part of the compositions according tothe invention is modified by a polar monomer. The compositions accordingto the invention can therefore contain unmodified PP and modified PP. Ingeneral, at least 50% by weight of the PP present in the compositionsaccording to the invention is modified by a polar monomer and,preferably, at least 80% by weight, to ensure an optimum compatibilitywith the PA also present in the compositions. For convenience reasonsand because it is an easy means of obtaining PPs which have the highmelt flow indices characteristic of the invention, it is furtherpreferred that all the PP present in the compositions be modified.

PP modified by means of polar monomers is intended to refer to PPscomprising units derived from polar monomers, in addition to the monomerunits defined above.

The polar monomers used to modify the PP may be any organic compoundscontaining at least one unsaturated bond, preferably of olefinic type,and at least one carboxylic group, optionally in anhydride form.

Monomers containing from 3 to 12 carbon atoms in their molecule arepreferably employed. These polar monomers may be especially unsaturatedmonocarboxylic acids such as acrylic, methacrylic or chloroacrylicacids, or unsaturated polycarboxylic acids such as maleic, fumaric anditaconic acids, or else anhydrides derived from these acids, such asmaleic anhydride. The preferred polar monomers are acrylic andmethacrylic acids and maleic anhydride. The best results are obtainedwith maleic anhydride.

The quantity of polar monomers modifying the PP is generally between0.002 and 20% by weight of PP employed. It is usually preferred thatthis quantity be between 0.01 and 10%, the best results being obtainedbetween 0.05 and 5%.

Where the structure of this modified PP is concerned, preference isgiven to graft copolymers in which the main chain (or backbone) ispolyolefinic (polypropylenic) in structure, and the side chains (orgrafts) are derived from polar monomers.

These graft copolymers may be manufactured by any known graftingtechniques such as grafting in solution, by irradiation or in thepresence of initiators, and grafting by melt-compounding, the latterbeing preferred. The grafting reaction is advantageously performed inthe presence of free radicals which can be generated by any of the knowntechniques for this purpose, such as irradiation or ozonization. Theoperation is usually performed at elevated temperature (for examplebetween 180° and 270° C.) and, preferably, in the presence of compoundsreleasing free radicals under the action of heat. Most particularly, itis preferred to work in the presence of organic peroxide compounds whichhave a decomposition temperature higher than 130° C. Examples ofperoxide compounds which can be employed are2,5-dimethyl-2,5-di(tert-butylperoxy)hexane,2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne, di-tert-butyl peroxide,tert-butyl hydroperoxide,alpha,alpha,-di(tert-butylperoxy)diisopropylbenzene and dicumylperoxide. The abovementioned peroxides are generally employed in aproportion of 0.01 g to 20 g per kg of PP used. Quantities of between0.05 and 10 g/kg and preferably of those between 0.1 and 5 g/kg areusually employed.

The weight ratio of the PAs to the PPs in the compositions according tothe invention is generally between 95/5 and 55/45, preferably between90/10 and 60/40. PA/PP ratios which are particularly preferred are thosebetween 75/25 and 65/35.

The MFI of the PP contained in the compositions according to theinvention constitutes an essential characteristic thereof. Theexpression "MFI of the PP" is intended to denote the melt flow indexmeasured (ASTM standard D 1238-86; 230/2.16 conditions) on all the PPsto be incorporated in the compositions. This implies that if severaldifferent PPs are incorporated, for example a modified portion and anunmodified portion, an MFI measurement is performed on each of the PPsto be incorporated; the "MFI of the PP" will then be the weighted meanof the various measured MFIs. It is appropriate to emphasize,nevertheless, that for convenience reasons it is preferred that the MFIsof the PPs to be incorporated into the compositions do not differ fromeach other by more than ten units.

This MFI must be higher than 20 g/10 min, it is preferably higher than50 g/10 min. The upper value of the MFI is limited only by the practicalpossibility of its being incorporated properly into the compositionsaccording to the invention. This value can be determined for eachindividual composition by a person skilled in the art, without excessiveexperimentation.

The best compromise of mechanical properties and of adhesivenessproperties is obtained when the MFI of the PP is such that 50 g/10 <minMFI of the PP<100 g/10 min, most particularly when this MFI is such that70 g/10 min ≦MFI of the PP ≦80 g/10 min.

The compatibilized compositions according to the invention may alsocontain one or more supplementary ingredients among those describedbelow.

They may contain a fibrous reinforcing agent such as, for example, glassfibres, carbon fibres, metal carbide or boride fibres, whiskers, etc. Apreferred fibrous reinforcing agent consists of glass fibres, optionallytreated with conventional coupling agents. Silanes may be mentioned assuch agents.

When a fibrous reinforcing agent is incorporated into the compositionsaccording to the invention, it may constitute from 10 to 80% of thetotal weight of these compositions, and preferably from 20 to 70% byweight. The best results are recorded when the fibrous reinforcing agentconstitutes from 35 to 65% of the total weight of the compositions.

Besides the PA, the at least partially modified PP and the optionallyfibrous reinforcing agent, the compositions according to the inventionmay also contain conventional additives chosen from those listed below,no limitation being implied:

inorganic fillers,

flame retardants,

antistatic agents,

colorants,

pigments,

mould release agents,

and the like.

The compositions may also contain conventional nucleating agents for thePA constituent, such as talc or alkali and alkaline-earth metalphosphinates; when the PA contained in the compositions is PAMXD6, awell-known nucleating agent is polyhexamethylene adipamide (nylon 66).

Finally, the compositions may contain stabilizers (against heat, light,antioxidants, etc.) which are conventional in PP and in PA.

The compatibilized compositions of the invention may be prepared by anyof the known techniques ensuring an intimate mixing of theirconstituents. Thus, the PA, the PP, the optional fibrous reinforcingagent and the optional other additives may be mixed dry and thenmelt-compounded. To carry out the dry mixing, it is possible to employany mixer, such as ribbon blenders, drum mixers or the rapid mixersmarketed by Henschel, Loedige, Dyosna and other companies. To carry outthe melt-compounding, the work can be done equally well in mixers of theexternal type or in mixers of the internal type, such as those marketedby Troester, Banbury and other companies. For technical and economicalreasons it is preferred, however, to work in mixers of the internal typeand more particularly in extruders, which constitute a particular classof internal mixers. These extruders may be single-screw extruders ortwin-screw extruders. The melt-compounding is generally carried outbetween 200° and 320° C., preferably between 240° and 280° C., forperiods of between 5 seconds and 30 minutes, preferably between 30seconds and 15 minutes.

In an alternative form of the process described above, the optionalfibrous reinforcing agent may be added, for example, to the previouslycompounded and molten mixture of PA and of PP and the melt-compoundingmay be continued in the presence of the reinforcing agent.

The compatibilized compositions of the invention may be processedgenerally in powder form or in the form of granules according to any ofthe known conventional methods: by injection moulding, by extrusion, bypressing, and the like.

According to another of its aspects, the invention also relates toadhesive composites of the compatibilized compositions described abovewith other materials capable of resulting in coherent and mechanicallystrong composites with these compositions. These other materials aregenerally chosen from organic synthetic polymers, cellulosic products,such as paper, cardboard and the like, and metals.

These other materials are preferably chosen from organic syntheticpolymers, particularly polymers which can be shaped using the techniquesfor processing thermoplastic polymers. These polymers may optionallycontain any of the other conventional additives already listed inrelation to the compatibilized compositions.

These organic synthetic polymers may be conventional thermoplasticpolymers such as vinyl chloride polymers and copolymers, styrenepolymers and copolymers and polymers and copolymers of alpha-monoolefinssuch as ethylene and propylene.

These organic synthetic polymers may also be chosen from the polymerscalled "thermoplastic elastomers", that is to say polymeric materials ofheterophase type consisting of a rubbery matrix in which there are rigidregions.

At ambient temperature these rigid regions replace the vulcanizationbridges which provide the elastic properties in conventional elastomers,and at elevated temperature (that is to say above the meltingtemperature of the crystalline phase) their disappearance permits anormal thermoplastic rheology, consequently enabling these materials tobe processed according to the traditional techniques applicable tothermoplastic polymers (extrusion, injection and the like), which aremuch simpler and faster than techniques using vulcanization.

The thermoplastic elastomers which can be employed for producing thecomposites may be chosen from

block copolymers containing rigid polyurethane blocks and flexibleblocks made up of polyether chains or of polyesters ending in hydroxylgroups; the products Desmopan from Bayer and Estane from Goodrich may bementioned as examples of these copolymers;

styrene copolymers containing rigid polystyrene in blocks interrupted byflexible polybutadiene, polyisoprene or ethylene-propylene elastomerblocks; the products Kraton and Cariflex from Shell and the productsSolprene from Phillips Petroleum may be mentioned as examples of thesecopolymers;

block copolymers containing rigid aromatic polyester blocks and flexibleblocks consisting of polyethers ending in alcohol functional groups; DuPont's Hytrel products may be mentioned as examples of these copolymers;

olefinic thermoplastic elastomers (called OTE hereinafter), which aremechanical mixtures of crystalline polyolefins such as polyethylene andpolypropylene and of olefinic elastomers such as elastomeric co- andterpolymers of ethylene, propylene and an optional diene like1,4-hexadiene, these elastomers being optionally partially crosslinked;by way of examples of these OTEs there may be mentioned the products TPRfrom Uniroyal, Telcar from Goodrich, Nordel TP from Du Pont, Dutral TPfrom Montedison and Santoprene from Monsanto; and

ionomeric elastomers such as, for example, the sulphonated andneutralized unsaturated olefinic elastomers, called "thionic polymers"by Exxon.

Among all the synthetic organic polymers listed above it is preferred toproduce the adhesive composites with those containing propylene-derivedunits, in particular with thermoplastic propylene homopolymers andcopolymers and with OTEs containing approximately 25 to approximately50% by weight of crystalline polypropylene, the latter making itpossible to obtain adhesive composites with remarkable properties withgreat ease.

The adhesive composites of the invention may contain the compatibilizedcompositions described above and the other materials in any proportions.In general, the compatibilized compositions and the other materials arepresent in the adhesive composites of the invention in proportions byweight of between 5/95 and 95/5, preferably between 20/80 and 80/20.

To produce the adhesive composites of the invention, the compatibilizedcompositions and the other materials can be bonded by any conventionalmethod. In particular, these compositions and these other materials maybe bonded by pressing, by coinjection, by overinjection of one onto theother, by coextrusion, and the like. Using the same methods, theseadhesive composites may be shaped into objects such as injectedarticles, extruded articles, profiles, seals with elastomericproperties, products with "barrier" properties (by virtue of thepresence of the PA), composite materials, and the like.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The examples which follow are used to illustrate the invention.

EXAMPLE 1

A compatibilized composition is prepared by dry mixing with each otherthe following constituents in the proportions shown:

7.8 parts by weight of PAMXD6 with a relative viscosity (measured in theform of a solution containing 10 g/1 at

25° C. in 96% by weight sulphuric acid) of 2.1

3.0 parts by weight of nylon 66,

0.6 parts by weight of talc,

0.1 parts by weight of barium stearate (lubricant),

55 parts by weight of glass fibres (GF) marketed by Owens Corning underthe name CS R 17 BX 1, and

13.5 parts by weight of PP modified by grafting with 1% by weight ofmaleic anhydride and whose MFI is 70 g/10 min.

Test specimens are injection-moulded from the above compositions todetermine their tensile strength according to ASTM standard D 638 andtheir resilience according to ASTM standard D 256. These determinationsgive the following results: tensile strength test:

strength:158.3 MPa

modulus:16.37 GPa

resilience test:79.1 J/m

The compatibilized composition described above is injection-moulded inthe form of a plaque (a). Separately, an olefinic thermoplasticelastomer marketed by Monsanto under the name Santoprene 121-73 - S 108is also converted into a plaque (b) pressed at 180° C. in a Lafargepress (30-tonne model) at a pressure of 4 MPa for 1 minute.

Plaque (a) (length: 125 mm, width: 125 mm, thickness 2 mm) and plaque(b) (length: 200 mm, width: 110 mm, thickness: 2 mm) are pressed in thesame press at 220° C. at a pressure of 3 MPa for 1 minute.

The composite resulting from the combination of the plaques (a) and (b)is cut into test specimens 200 mm in length and 25 mm in width. Thecontact surface, therefore, represents a rectangle of 125×25 mm. Thetest specimens are kept at ambient temperature for 24 hours. Anadhesiveness test is carried out according to BS (British Standard)5350, part C 11 on these test specimens with a pull speed of 100 mm/minuntil failure by loss of adhesion of the parts in contact.

The results of this test are cited below (mean of 3 measurements):

adhesive strength (N): 29.3

adhesive strength per unit length (N/m): 1171

EXAMPLES 2, 3 and 4R

(Examples 2 and 3 illustrate the invention; Example 4R is provided byway of comparison).

Compatibilized compositions are prepared by dry mixing with each otherthe same constituents as in Example 1, except that the PAMXD6 employedhas a relative viscosity of 3.5.

In addition:

in Example 2, the modified PP is the same as that employed in Example 1;

in Example 3, the modified PP contains 1% of maleic anhydride and has anMFI of 25 g/10 min; and

in Example 4R (for comparison), the modified PP contains 1% of maleicanhydride and has an MFI of 9 g/10 min.

The Table below mentions the quantities of various constituents used toprepare the compatibilized compositions of these examples, themechanical properties of these compositions, measured as shown inExample 1, and the results of the adhesiveness test, carried out asdescribed in Example 1.

                  TABLE                                                           ______________________________________                                        Examples          2       3         4R                                        ______________________________________                                        Nature and quantity (parts by                                                 weight) of the constituents                                                   used:                                                                         PAMXD6            30.2    28.9      30.2                                      Nylon 66          3.9     5.0       3.9                                       Talc              0.8     1.0       0.8                                       Barium stearate   0.1     0.1       0.1                                       GF                50      50        50                                        Modified PP       15      15        15                                        MFI of the modified PP                                                                          70      25        9                                         (g/10 min)                                                                    Mechanical properties:                                                        1. Tensile strength                                                           strength (MPa)    158.5   148,4     113.5                                     modulus (GPa)     17.01   16.80     16.42                                     2. Resilience (J/m)                                                                             101     80        75                                        Adhesiveness test:                                                            Adhesive strength (N)                                                                           19.9    12.7      5.5                                       Adhesive strength per unit                                                                      795     510       219                                       length (N/m)                                                                  ______________________________________                                    

The results collated in this table show that, all other conditionsremaining similar, the compatibilized compositions containing a PP ofhigh MFI according to the invention exhibit a superior compromise ofmechanical properties and of adhesiveness properties.

EXAMPLE 5R

This example is given by way of comparison.

A composition is prepared as described in Examples 2 to 4R, but withoutincorporating the modified PP.

A plaque injection-moulded from this composition, is pressed onto aplaque of the Santoprene product, as shown in Example 1, and theresulting composite is subjected to an adhesiveness test. The measuredadhesive strength is nil.

What is claimed is:
 1. A compatibilized composition, comprising:at least one polyamide; and at least one propylene polymer which is at least partially modified by a polar monomer and which has a melt flow index (MFI) measured according to ASTM standard D 1238-86 (230/2.16 conditions) such that 70 g/10 min.≦MFI of the propylene polymer≦80 g/10 min.
 2. The compatibilized composition according to claim 1, wherein the at least one polyamide is a polycondensation reaction product of xylylenediamine and an alpha,omega-dicarboxylic linear aliphatic acid containing from 6 to 12 carbon atoms.
 3. The compatibilized composition according to claim 1, wherein the at least one propylene polymer is a polymer containing at least 80% of propylene-derived monomer units.
 4. The compatibilized composition according to claim 1, wherein the modified propylene polymer is a maleic anhydride graft copolymer.
 5. The compatibilized composition according to claim 1, wherein the at least one polyamide and the at least one propylene polymer are present in a weight ratio ranging between 90 to 10 and 60 to
 40. 6. The compatibilized composition according to claim 1, additionally containing a fibrous reinforcing agent.
 7. The compatibilized composition according to claim 6, wherein the fibrous reinforcing agent consists of glass fibers incorporated in a proportion ranging from 10 to 80% by weight relative to total weight of the compatibilized composition.
 8. The compatibilized composition according to claim 1, wherein the MFI is a weighted mean of each of the at least one propylene polymer when there is more than one of same.
 9. The compatibilized composition according to claim 2, wherein the at least one polyamide is a polycondensation product of m-xylylenediamine with adipic acid and has a relative viscosity, measured as a solution containing 10 g/l at 25° C. in 96% by weight sulfuric acid, which does not exceed
 4. 10. The compatibilized composition according to claim 2, wherein the at least one propylene polymer is a polymer containing at least 80% of propylene-derived monomer units.
 11. The compatibilized composition according to claim 2, wherein the modified propylene polymer is a maleic anhydride graft copolymer.
 12. The compatibilized composition according to claim 2, wherein the at least on polyamide and the at least one propylene polyamide are present in a weight ratio ranging between 90 to 10 and 60 to
 40. 13. The compatibilized composition according to claim 3, wherein the modified propylene polymer is a maleic anhydride graft copolymer.
 14. The compatibilized composition according to claim 3, wherein the at least on polyamide and the at least one propylene polymer are present in a weight ratio ranging between 90 to 10 and 60 to
 40. 15. The compatibilized composition according to claim 4, wherein the at least on polyamide and the at least one propylene polymer are present in a weight ratio ranging between 90 to 10 and 60 to
 40. 